The technical field of this invention is phototherapy and, in particular, instruments employing optical fibers or other flexible light waveguides to deliver radiation to a targeted biological sight.
Fiber optic phototherapy is a increasing popular modality for the diagnosis and/or treatment of a wide variety of diseases. For example, in surgery, infrared laser radiation will often be delivered to a surgical site via a hand-held instrument incorporating an optically transmissive fiber in order to coagulate blood vessels or cauterize tissue. Similar fiber optic delivery systems have been proposed for endoscopic or catheter-based instruments to deliver therapeutic radiation to a body lumen or cavity. U.S. Pat. No. 4,336,809 (Clark) and U.S. Reissue Pat. No. RE 34,544 (Spears) disclose that hematoporphyrin dyes and the like selectively accumulate in tumorous tissue and such accumulations can be detected by a characteristic fluorescence under irradiation with blue light. These patents further teach that cancerous tissue that has taken up the dye can be preferentially destroyed by radiation (typically high intensity red light) that is absorbed by the dye molecules during phototherapy.
Others have proposed the use of fiber-delivered radiation to treat artherosclerotic disease. For example, U.S. Pat. No. 4,878,492 (Sinofsky et al.) discloses the used of infrared radiation to heat blood vessel walls during balloon angioplasty in order to fuse the endothelial lining of the blood vessel and seal the surface. Another application of fiber-delivered radiation is disclosed in U.S. Pat. No. 5,053,033 (Clarke) which teaches that restenosis following angioplasty can be inhibited by application of UV radiation to the angioplasty site to kill smooth muscle cells which would otherwise proliferate in response to angioplasty-induced injuries to blood vessel walls.
In yet another application, phototherapeutic instruments are employed to treat electrical arrhythmia of the heart. In such applications, a catheter having a fiber optic component is fed via a major artery into a patient's heart. Once inside the heart, a catheter senses electrical impulses with electrical contacts on its outer sheath or other catheter elements in order to locate the source of arrhythmia. Once located, the phototherapeutic component is activated to "ablate" a portion of the inner heart wall. By coagulating the tissue in the vicinity of the arrhythmia source, the likelihood that the parent's heart will continue to experience arrhythmia is thus reduced.
In other applications, laser radiation can be used in conjunction with a similar catheter instrument inside a patient's heart to increase blood flow to oxygen starved regions of the heart muscle. In such procedures, the laser radiation is used to form small holes into the heart muscle so that the oxygen-depleted tissue is bathed with blood from the ventricular cavity.
In all of these applications, there is the potential for damage to the patient's internal organs, especially the heart, if the light-emitting fiber is inserted too far into the patient's tissue. Particularly, in the case of the heart muscle, perforation of the heart wall can have very dangerous effects.
Accordingly, there exists a need for better apparatus for fiber-optic phototherapy. In particular, devices that can "stop" an optical fiber from perforating a patient's organs would meet a particularly important need in the field of minimally-invasive phototherapeutic surgery. Moreover, a device that can help stabilize the phototherapeutic instrument in operation (such as within the chambers of a rapidly beating heart) would also be particularly useful.